Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
A body-mountable device, such as a contact lens or wrist-mounted device, can include sensors or other devices that are configured to detect one or more physiological or health-related parameters, including blood pressure, pulse rate, body temperature, glucose level, blood oxygen concentration, etc. In some cases, it may also be useful to know or track the geographical or proximate location or other contextual or environmental factors of a wearer of a body-mountable device. However, these devices may be too small, low in profile, or power sensitive to include on-board GPS or other location-tracking systems.